Urban heat mitigation strategies

Abstract

Urban heat has been detected in many cities worldwide and has negatively impacted the urban environment and human well-being. Many strategies have been developed to mitigate urban heat, collectively called urban heat mitigation strategies (UHMSs). This study reviewed the four types of passive UHMSs (i.e., greenery, cool materials, evaporation techniques, and shading devices) from an implementation perspective to support urban heat mitigation. The definitions, mitigation performance, planning and design variables, and cost-benefits of these UHMSs are elaborated from three categories, according to the place of application: private realm, public realm, and combinations. The results show that green infrastructures have high performance in cooling and energy saving in private and public realms, and their effectivenesses are affected by many factors, such as vegetation species. For cool materials, reflective materials generally have higher cooling potentials and lower costs than heat storage materials and heat harvesting materials. The predominant planning and design variables for cooling effectiveness are the colour and construction materials, and coating materials. The evaporation techniques can reduce ambient temperature significantly due to the high cooling potential of latent heat. The main variables include water flow rate, water particle size, area and shape of water bodies etc. To achieve optimal cooling performance, it is required to properly define the surface temperature of the evaporative cooling pads for evaporative cooling towers and shading structures and slat angles for shading. Also, UHMS combinations can have higher mitigation performance than a single one. All these findings help decision-makers better understand the implementation of UHMS in detail, supporting the proper selection and application of strategies for urban heat mitigation.